Recording eight digital audio channels on a single magneto optical disk

ABSTRACT

A method and apparatus for recording onto or playing back from a magneto optical disk eight channels of digital audio data. Eight channels of serial audio data, for example in a AES/EBU format is converted to parallel data and provided to one or more buffers via a DMA controller. After buffering, the data may be recorded onto a MO disk via an SCSI.

FIELD OF THE INVENTION

This invention relates to the recording of digital audio data on amagneto optical disk (MO). More specifically, this invention relates toan improved method and apparatus for recording eight channels of digitalaudio data on a single MO disk.

BACKGROUND OF THE INVENTION

In the field of data recording, various recording devices are used whichincorporate different technologies. In the audio recording field,digital audio tape (DAT) recording technology is widely used. When thistechnology is employed, generally four channels of information aresimultaneously recorded on the tape medium.

While providing an improvement in recording quality over previoustechnology, DAT still suffers from some drawbacks. First, there is aslow access time in playing back recorded data. A second relateddrawback is the difficulty in skipping tracks for editing or playback.Moreover, the use of only four channels limits sound quality.

Outside the audio recording field, magneto optical (MO) disks have beendeveloped for the storage and playback of digital data. Magneto opticaldisks provide at least two advantages over storage systems using a tapestorage medium. First, the information stored on the MO disk may beaccessed much more rapidly than can information stored on a taperecording medium. Secondly, the MO disk provides the capability of"slipping" tracks in time.

However, wider use of MO recording has heretofore been limited becauseof the relatively slow transfer rate of data from the MO disk controllerto the MO disk itself, and the relatively fast rate of data acquisitionfrom the source to be recorded. The discrepancy in speed of these twofunctions have made it difficult to apply this technology to otherfields, such as audio recording.

Hence, there is a need to provide a recording device which provides theease of use afforded by magneto optical disk-based recording systems.There is a further need to improve recording quality by simultaneouslyrecording more than four tracks of data on a recording medium.

SUMMARY OF THE INVENTION

A general object of this invention is to overcome these and otherdrawbacks of the prior art by providing a magneto optical disk recorderwhich is capable of recording eight tracks of data onto a magnetooptical disk. Accordingly, there is disclosed an apparatus for recordingand playing back digital audio signals comprising: input means forproviding a plurality of channels of digital audio signals; buffer meansfor storing digital data signals; a direct memory access (DMA)controller for coupling the plurality of channels of digital audiosignals to the buffer means; a magneto optical disk drive; and a smallcomputer system interface (SCSI) for operatively coupling the MO diskdrive with the DMA controller.

According to one aspect of the invention, the plurality of channels ofaudio data consists of eight channels of audio data.

According to another aspect of the invention, the input means includesmeans for converting the plurality of channels of audio data from serialdata to parallel data.

According to still another aspect of the invention, serial data isprovided to the apparatus in an AES/EBU format.

According to yet another aspect of the invention, the apparatus furtherincludes output means coupled to the MO disk drive through the SCSI andthe buffer means, the output means providing a plurality of channels ofaudio signals corresponding to a plurality of channels of audio datawhich has been stored on a MO disk.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of an audio recording system utilizing the presentinvention.

FIG. 2 is a block diagram showing an embodiment of the presentinvention.

FIG. 3 is a block diagram showing another embodiment of the presentinvention.

FIG. 4 is a block diagram showing yet another embodiment of the presentinvention.

FIGS. 5A-1 through 5A-3 and 5B-1 through 5B-3 are circuit diagramsshowing the embodiment of FIG. 4 in greater detail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an audio recording system which may be used forprofessional recording, for example. In this system, a digital mixer 10is coupled to various multichannel input devices 20 and variousmultichannel output devices 30. Each device operatively shares a commonSYNC signal 40. The input devices shown are a plurality of eight-channelplayer-recorders 20. A first player 22 is used to provide sound effectsto the digital mixer, while other players 24 and 26 provide dialog andmusic sweet, respectively, to the mixer 10. Once input to the mixer 10,these signals are processed in various ways as known in the art and canbe output to, for example, a plurality of multichannel recorders 32, 34,36. In the system shown, each of the player/recorders is an eightchannel device; that is, each device plays-back or records eightchannels simultaneously.

FIG. 2 is a block diagram of an eight channel player/recorder 100according to one embodiment of the invention, such as may be used in therecording system previously described. In the device shown, varioussignals, both input and output, are controlled by a central processingunit (CPU) 110 which is associated with both a volatile memory 112 and anon-volatile memory 114. In the example shown, the CPU has associatedwith it a random access memory (RAM) 112, as well as a read only memory(ROM) 114.

The recorder 100 is synchronized by means of SYNC signals provided to aCIK interface 118, for example a parallel input output (PIO) circuit.The SYNC signals may comprise, for example video 120, di-sync 122 andword sync 124 signals input to the recorder 100 via a clock circuit 126,as shown in FIG. 2. In this way, the recorder 100 may be synchronizedwith other devices which comprise a recording system, as in the exampleshown in FIG. 1.

The CPU 110 is used to control the flow of digital audio data input toand output from the recorder 100 via a digital audio interface 128. Thedigital audio data is input at four ports 130, 132, 134, and 136 to thedigital audio interface 128. Each port receives the data in AES/EBUformat. Thus, each port provides two channels of serial audio data.Together, the four ports provide four separate lines for providing eightaudio channels to the recorder device. Similarly, by using four audioOUT ports 138, 140, 142, and 144, eight channels of digital audiosignals may be output from the recorder 100. Digital audio data may alsobe converted to analog signals using a D/A converter 150, and the analogsignals output to an external monitoring device, such as a set ofheadphones 152.

The digital audio interface 128 may be controlled locally by a user viaa front panel 146 of the recorder 100, which may include various peakmeters, keys or jog wheels. These devices may provide a display of thestatus of the recorder. Moreover, input from these devices may be usedto control the recorder via a serial communication controller 148 (SCC).Alternatively, the recorder may include means for remote control anddisplay 158, including, for example a jog wheel, display, or keys.Further, the recorder 100 may be controlled using a user interface 150linked to the recorder 100 via a parallel input output (PIO) circuit152.

In a typical operation, eight channels of data are input from the fourIN ports. This input provides four sets of data in parallel which may beconveniently processed by the CPU. Each set of data contains twochannels of twenty four bit audio data for a total of eight channels.This data may be processed in the recorder 100 under control of the CPU110.

More specifically, according to one embodiment of the invention, theeight channels of digital audio signals may be recorded onto, orplayed-back from a magneto optical disk drive 154 via a small computersystem interface (SCSI) 156. In this example, the problems associatedwith a large data transfer rate and a relatively slow read/write rateare overcome by use of proper buffering and direct memory access (DMA)transfers. These features are explained with reference to FIG. 3.

Also shown in FIG. 2 are means for providing time code data to beassociated with the digital audio signals processed in the recorder 100.According to the embodiment shown, a time code interface circuit 164 maybe used to receive input time code data 162 or transmit output time codedata 160. Both the input 162 and output time code data 160 are coupledwith the CPU 110 through the time code interface circuit 164.

Further, the recorder 100 may be coupled to other external devicesthrough a serial communications controller (SCC) 170. The SCC 170permits the use of external devices 166 for expansion or diagnostics ofthe recorder. Other external devices may be coupled through a 9 pinconnector 168, as shown.

FIG. 3 shows a block diagram illustrating a preferred embodiment of theinvention. In a recording operation using the embodiment shown, eightchannels of digital audio signals are input to a digital audio interface200. The digital audio interface 200 converts the serial data toparallel data which can be processed more conveniently by a CPU 210.Such processing may be performed, for example, under control ofcrossfade control software 212. The conversion of the data may includeserror checking processing by means known in the art (not shown).

In order to overcome the difference in the transfer rate of the data andthe slower read/write rate, various buffers 220, 222, 224, and 226 areprovided. Accordingly, the parallel data is read into the buffers 220,222, 224, and 226 via a DMA controller 230. After being received into abuffer, the data can be provided to take SCSI 240 at the correct speed,as required by the particular MO drive 250 which is used. For example, atypical SCSI controller and MO drive may write 1.5 mbytes every second,while each read/write interval in which an eight channels (eight words)are read or written requires 20.83 μsec. Thus, if two buffers holding131,072 words (16 bytes) are used, the SCSI would require 174 msec towrite the contents of two buffers holding eight audio channels. However,different buffer sizes may be used as required as different MO driveswith various speeds are used.

The system shown in FIG. 3 may also be used in a similar manner for aplayback operation. That is, as the MO drive 250 reads digital audiodata from a MO disk, the data is provided to buffers 220, 222, 224, and226 from which it can be transferred via the DMA controller 230 to thedigital audio interface 200. The digital audio interface 200 convertsthe parallel data to serial data which may be output to other devices(not shown).

FIG. 4 is a block diagram illustrating an embodiment by which eightchannel serial audio data may be input into a recorder and converted toparallel data for processing or recording. Similarly, the embodimentdiscloses an example by which processed data or data read from a MO diskmay be converted to serial data to be output to other devices. In thisexample, serial data is input using the AES/EBU format 300. In the nextstage 310 of the circuit, the audio data bits of this thirty-two bitformat is separated from the other bits, such as sync bits and the audiosample validity bit, as known in the art. According to this embodiment,the data bits representing the audio signal may comprise twenty-fourbits of audio data, which are converted from a serial format to aparallel format by a serial to parallel converter circuit 330.

The control circuits for implementing the data separation 310 and S/Pconversion 330 are operated according to control signals originatingfrom a common clock circuit 320. The parallel data is then input alongwith associated address bits onto bus lines 340 which are operativelycoupled to a DMA controller and buffer circuits as well as to a CPU.

Parallel audio data, for example from various buffers, may be sent to aparallel to serial conversion circuit 350 and then encoded into AES/EBUformat by encoding circuits 360. The encoded data may then be providedto other output devices via a serial output 370.

This example is illustrating in greater detail in the circuit diagram ofFIGS. 5A and 5B in which common elements are indicated by the samereference numbers as in FIG. 4. In FIG. 5A, a three-pin connector 302provides a serial input which is properly isolated from the recorder, byvarious isolation means 304. The serial data in AES/EBU format istransmitted to an integrated circuit 312 which indicates transmissionerrors and identifies subframes based on data bits contained in theserial input signal.

The audio data is then provided to four integrated circuits 332, 334,336, and 338 which convert the serial data to parallel data. Theparallel audio data is then provided to data bus lines 342. In theexample shown, twenty four bits of audio data are provided by the S/Aconversion circuits 332, 334, 336 and 338.

FIG. 5B shows circuitry for providing parallel audio data as a serialoutput. Accordingly, bus lines 342 are coupled to four integratedcircuits 352, 354, 356, and 358 which are synchronized such thatparallel data is converted to a serial signal. Serial data signals maythen be encoded by use of an encoding integrated circuit 362. Once inAES/EBU format, serial signals are provided to a three-prong terminal372 with which other devices may be operatively coupled.

According to these embodiments of the invention, eight channels may beread or recorded using a magneto optical disk. Thus, recordersincorporating the invention may be used to more conveniently editvarious audio signals by utilizing the ease of access provided by a MOdisk. The invention is thus well suited to incorporation in audioproduction and video post-production facilities. Its many applicationsin film television, radio and audio recording production include librarystorage and retrieval, composition of commercials by an assemblyprocess, recording for acquisition of program material for use in anaudio work station, and playback of work station generated programmaterial.

The foregoing is a detailed description of the preferred embodiments.The scope of the invention, however, is not so limited. Variousalternatives will be readily apparent to one of ordinary skill in theart. The invention is only limited by the claims appended hereto.

What is claimed is:
 1. An apparatus for recording and playing backdigital audio signals comprising:input means for providing a pluralityof channels of digital audio signals; buffer means for storing digitaldata signals; a direct memory access (DMA) controller for coupling theplurality of channels of digital audio signals to the buffer means; amagneto optical disk drive; and a small computer system interface (SCSI)for operatively coupling the MO disk drive with the DMA controller;wherein the plurality of channels of digital audio signals is stored bythe buffer means and provided to the MO disk drive; wherein the inputmeans includes means for converting the plurality of channels of audiodata from serial data to parallel data; and wherein serial data isprovided to the apparatus in AES/EBU format.
 2. The apparatus of claim 1further including output means coupled to the MO disk drive through theSCSI and the buffer means, the output means providing a plurality ofchannels of audio signals corresponding to a plurality of channels ofaudio data which has been stored on a MO disk.
 3. A method of recordingand playing back digital audio signals comprising:providing a pluralityof channels of digital audio signals to a player/recorder apparatus;coupling the plurality of channels of digital audio signals to a directmemory access (DMA) controller; storing the plurality of channels ofdigital audio signals in one or more buffers under control of the DMAcontroller; providing the digital audio data signals from the buffer orbuffers to a magneto optical disk drive via a small computer systeminterface (SCSI); and recording the digital audio signals onto a magnetooptical disk; wherein the step of providing a plurality of channels ofdigital audio signals to a player/recorder includes converting theplurality of channels of audio data from serial data to parallel data;and wherein serial data is provided to the apparatus in AES/EBU format.4. The method of claim 3 further including providing from the apparatusa plurality of channels of audio signals corresponding to a plurality ofchannels of audio data which have been stored on said magneto opticaldisk.
 5. An apparatus for recording and playing back digital audiosignals comprising:a small computer system interface (SCSI) forcontrolling a magneto optical disk drive; and input means for providinga plurality of channels of digital audio signals; a direct memory access(DMA) controller for coupling the plurality of channels of digital audiosignals to the SCSI whereby digital signal corresponding to theplurality of channels of digital audio signals are provided to themagneto optical disk drive; wherein the input means includes means forconverting the plurality of channels of audio data from serial data toparallel data; and wherein serial data is provided to the apparatus inAES/EBU format.
 6. The apparatus of claim 5 further including outputmeans coupled to the MO disk drive through the SCSI and the buffermeans, the output means providing a plurality of channels of audiosignals corresponding to a plurality of channels of audio data which hasbeen stored on a MO disk.